usr.bin/make/hash.c

/*
 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
 * Copyright (c) 1988, 1989 by Adam de Boor
 * Copyright (c) 1989 by Berkeley Softworks
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)hash.c      5.5 (Berkeley) 12/28/90";
#endif /* not lint */

/* hash.c --
 *
 *      This module contains routines to manipulate a hash table.
 *      See hash.h for a definition of the structure of the hash
 *      table.  Hash tables grow automatically as the amount of
 *      information increases.
 */

#include "sprite.h"
#include "hash.h"

/*
 * Forward references to local procedures that are used before they're
 * defined:
 */

static void             RebuildTable();

/*
 * The following defines the ratio of # entries to # buckets
 * at which we rebuild the table to make it larger.
 */

#define rebuildLimit 8

/*
 *---------------------------------------------------------
 *
 * Hash_InitTable --
 *
 *      This routine just sets up the hash table.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Memory is allocated for the initial bucket area.
 *
 *---------------------------------------------------------
 */

void
Hash_InitTable(t, numBuckets)
        register Hash_Table *t; /* Structure to use to hold table. */
        int numBuckets;         /* How many buckets to create for starters.
                                 * This number is rounded up to a power of
                                 * two.   If <= 0, a reasonable default is
                                 * chosen. The table will grow in size later
                                 * as needed. */
{
        register int i;
        register struct Hash_Entry **hp;

        /*
         * Round up the size to a power of two.
         */
        if (numBuckets <= 0)
                i = 16;
        else {
                for (i = 2; i < numBuckets; i <<= 1)
                         /* void */ ;
        }
        t->numEntries = 0;
        t->size = i;
        t->mask = i - 1;
        t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
        while (--i >= 0)
                *hp++ = NULL;
}

/*
 *---------------------------------------------------------
 *
 * Hash_DeleteTable --
 *
 *      This routine removes everything from a hash table
 *      and frees up the memory space it occupied (except for
 *      the space in the Hash_Table structure).
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Lots of memory is freed up.
 *
 *---------------------------------------------------------
 */

void
Hash_DeleteTable(t)
        Hash_Table *t;
{
        register struct Hash_Entry **hp, *h, *nexth;
        register int i;

        for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
                for (h = *hp++; h != NULL; h = nexth) {
                        nexth = h->next;
                        free((char *)h);
                }
        }
        free((char *)t->bucketPtr);

        /*
         * Set up the hash table to cause memory faults on any future access
         * attempts until re-initialization.
         */
        t->bucketPtr = NULL;
}

/*
 *---------------------------------------------------------
 *
 * Hash_FindEntry --
 *
 *      Searches a hash table for an entry corresponding to key.
 *
 * Results:
 *      The return value is a pointer to the entry for key,
 *      if key was present in the table.  If key was not
 *      present, NULL is returned.
 *
 * Side Effects:
 *      None.
 *
 *---------------------------------------------------------
 */

Hash_Entry *
Hash_FindEntry(t, key)
        Hash_Table *t;          /* Hash table to search. */
        char *key;              /* A hash key. */
{
        register Hash_Entry *e;
        register unsigned h;
        register char *p;

        for (h = 0, p = key; *p;)
                h = (h << 5) - h + *p++;
        p = key;
        for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
                if (e->namehash == h && strcmp(e->name, p) == 0)
                        return (e);
        return (NULL);
}

/*
 *---------------------------------------------------------
 *
 * Hash_CreateEntry --
 *
 *      Searches a hash table for an entry corresponding to
 *      key.  If no entry is found, then one is created.
 *
 * Results:
 *      The return value is a pointer to the entry.  If *newPtr
 *      isn't NULL, then *newPtr is filled in with TRUE if a
 *      new entry was created, and FALSE if an entry already existed
 *      with the given key.
 *
 * Side Effects:
 *      Memory may be allocated, and the hash buckets may be modified.
 *---------------------------------------------------------
 */

Hash_Entry *
Hash_CreateEntry(t, key, newPtr)
        register Hash_Table *t; /* Hash table to search. */
        char *key;              /* A hash key. */
        Boolean *newPtr;        /* Filled in with TRUE if new entry created,
                                 * FALSE otherwise. */
{
        register Hash_Entry *e;
        register unsigned h;
        register char *p;
        int keylen;
        struct Hash_Entry **hp;

        /*
         * Hash the key.  As a side effect, save the length (strlen) of the
         * key in case we need to create the entry.
         */
        for (h = 0, p = key; *p;)
                h = (h << 5) - h + *p++;
        keylen = p - key;
        p = key;
        for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
                if (e->namehash == h && strcmp(e->name, p) == 0) {
                        if (newPtr != NULL)
                                *newPtr = FALSE;
                        return (e);
                }
        }

        /*
         * The desired entry isn't there.  Before allocating a new entry,
         * expand the table if necessary (and this changes the resulting
         * bucket chain).
         */
        if (t->numEntries >= rebuildLimit * t->size)
                RebuildTable(t);
        e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
        hp = &t->bucketPtr[h & t->mask];
        e->next = *hp;
        *hp = e;
        e->clientData = NULL;
        e->namehash = h;
        (void) strcpy(e->name, p);
        t->numEntries++;

        if (newPtr != NULL)
                *newPtr = TRUE;
        return (e);
}

/*
 *---------------------------------------------------------
 *
 * Hash_DeleteEntry --
 *
 *      Delete the given hash table entry and free memory associated with
 *      it.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Hash chain that entry lives in is modified and memory is freed.
 *
 *---------------------------------------------------------
 */

void
Hash_DeleteEntry(t, e)
        Hash_Table *t;
        Hash_Entry *e;
{
        register Hash_Entry **hp, *p;

        if (e == NULL)
                return;
        for (hp = &t->bucketPtr[e->namehash & t->mask];
             (p = *hp) != NULL; hp = &p->next) {
                if (p == e) {
                        *hp = p->next;
                        free((char *)p);
                        t->numEntries--;
                        return;
                }
        }
        (void) write(2, "bad call to Hash_DeleteEntry\n", 29);
        abort();
}

/*
 *---------------------------------------------------------
 *
 * Hash_EnumFirst --
 *      This procedure sets things up for a complete search
 *      of all entries recorded in the hash table.
 *
 * Results:
 *      The return value is the address of the first entry in
 *      the hash table, or NULL if the table is empty.
 *
 * Side Effects:
 *      The information in searchPtr is initialized so that successive
 *      calls to Hash_Next will return successive HashEntry's
 *      from the table.
 *
 *---------------------------------------------------------
 */

Hash_Entry *
Hash_EnumFirst(t, searchPtr)
        Hash_Table *t;                  /* Table to be searched. */
        register Hash_Search *searchPtr;/* Area in which to keep state
                                         * about search.*/
{
        searchPtr->tablePtr = t;
        searchPtr->nextIndex = 0;
        searchPtr->hashEntryPtr = NULL;
        return Hash_EnumNext(searchPtr);
}

/*
 *---------------------------------------------------------
 *
 * Hash_EnumNext --
 *    This procedure returns successive entries in the hash table.
 *
 * Results:
 *    The return value is a pointer to the next HashEntry
 *    in the table, or NULL when the end of the table is
 *    reached.
 *
 * Side Effects:
 *    The information in searchPtr is modified to advance to the
 *    next entry.
 *
 *---------------------------------------------------------
 */

Hash_Entry *
Hash_EnumNext(searchPtr)
        register Hash_Search *searchPtr; /* Area used to keep state about
                                            search. */
{
        register Hash_Entry *e;
        Hash_Table *t = searchPtr->tablePtr;

        /*
         * The hashEntryPtr field points to the most recently returned
         * entry, or is nil if we are starting up.  If not nil, we have
         * to start at the next one in the chain.
         */
        e = searchPtr->hashEntryPtr;
        if (e != NULL)
                e = e->next;
        /*
         * If the chain ran out, or if we are starting up, we need to
         * find the next nonempty chain.
         */
        while (e == NULL) {
                if (searchPtr->nextIndex >= t->size)
                        return (NULL);
                e = t->bucketPtr[searchPtr->nextIndex++];
        }
        searchPtr->hashEntryPtr = e;
        return (e);
}

/*
 *---------------------------------------------------------
 *
 * RebuildTable --
 *      This local routine makes a new hash table that
 *      is larger than the old one.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The entire hash table is moved, so any bucket numbers
 *      from the old table are invalid.
 *
 *---------------------------------------------------------
 */

static void
RebuildTable(t)
        register Hash_Table *t;
{
        register Hash_Entry *e, *next, **hp, **xp;
        register int i, mask;
        register Hash_Entry **oldhp;
        int oldsize;

        oldhp = t->bucketPtr;
        oldsize = i = t->size;
        i <<= 1;
        t->size = i;
        t->mask = mask = i - 1;
        t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
        while (--i >= 0)
                *hp++ = NULL;
        for (hp = oldhp, i = oldsize; --i >= 0;) {
                for (e = *hp++; e != NULL; e = next) {
                        next = e->next;
                        xp = &t->bucketPtr[e->namehash & mask];
                        e->next = *xp;
                        *xp = e;
                }
        }
        free((char *)oldhp);
}